All eight GOP members of the Senate Environment and Public Works committee failed to show up at the meeting to consider the nomination of Gina McCarthy, who currently heads the EPA's air pollution office. Committee rules require at least two minority members to be present for a vote.

Republicans are demanding answers from the EPA on a range of transparency issues. But they aren't satisfied with the responses they've received.

Sen. Barbara Boxer, D-California, who heads the committee, urged Republicans to vote, or she said Democrats alone would advance McCarthy's bid.

White House spokesman Jay Carney, speaking to reporters on Air Force One en route to Texas, called on Republicans "to stop the theater and to move forward with the process."

Carney said there has been "an historic level of obstructionism" on McCarthy and other nominees.

House and Senate Republican leaders told Obama Thursday that they will refuse to nominate candidates to serve on an advisory board that is to play a role in holding down Medicare costs under the new health care act.

And on Wednesday, Republicans used a procedural move to delay a Senate panel from considering the confirmation of Obama's pick to the head the Labor Department.